The E-M1 has more of a "pro" build. Shutter life is longer, weather proofing extensive, the whole camera can be dropped, it can be roughed up, take years of abuse.

How do you know all this? How many years of abuse has any E-M1 taken?

All within limits of course, but it's clearly targetting the pro segment with its build. Oly is also sending a message to resilient 43 DSLR users that the E-M1 is a suitable replacement to their E1/E3/E5 which were "built like tanks".

The A7(r) is more... fragile.

In what way is it more fragile?

It looks quite substantial to me

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Bob

E-M1 build

As you can see. Quite a substantial difference. The A7 is somewhere around an EM-5 in terms of build.